If your wedding is just around the corner, why not combine the bachelor party and the bachelorette party? This way the couple can celebrate their last days of being single and their upcoming lifelong relationship with all their special friends. Combining the parties lets the members of the wedding party get to know one another.
Bar Hopping
Have everyone go to the same bars. Have contests between the bachelor's group and the bachelorette's group, such as who can get the most phone numbers, who can get the most drinks bought for him, or who can get her T-shirt signed by the most members of the opposite sex.
Las Vegas Trip
Have both groups go to Las Vegas. Enjoy dining, hanging out at the hotel pool, gambling, and even going to clubs together. You could have everyone compete in a blackjack or poker tournament, with a special prize for the person who lasts the longest in the tournament.
Strip Club
Strip clubs do not discriminate based on sex. So have both the bachelor's friends and the bachelorette's friends go to strip clubs together. The night could be split between male and female strip clubs. Who knows, maybe a bachelorette will even buy a bachelor a lap dance, or vice versa.
Scavenger Hunt
Create a scavenger hunt list. Split the groups up into teams or pairs, if you like. Have everyone meet later that evening at a restaurant and determine the winner while enjoying a nice meal together and drinks for anyone wishing to drink.